Question

It is known that chloroplastic glutamine synthetase mutants of barley grow normally under conditions suppressing photorespiration (1% CO2) but cannot survive under conditions that do not suppress photorespiration (0.03% CO2). Explain why this phenomenon is observed.

Answer 1

The enzyme glutamine synthetase convert glutamate to glutamine. It can help the nitrogen metabolism process in plants. The enzyme need sufficient ammonium group and ATP to function. If the enzyme is non functional it does not require any ATP for its functions. So there is sufficient ATP supply for the photorespiration process. We know the barley plant is a C4 plant. The tree which has higher photorespiration rate can get sufficient CO2 from photorespiration process. Hence though there is higher photorespiration rate the barley plant thus get sufficient CO2 from photorespiration not from the environment.